EPB machine S66 was launched on the 1km-long drive southwards from Finance Centre Station (Finans Merkezi) in mid-March – along with sister machine (S65) which launched a month later – and has been achieving consistently good advance rates of up to 28 rings (42m) per day. Average advance rates of 20 rings per day over a ten-day period have been achieved with both machines, despite the challenges from Covid-19 and the city in lockdown. However, coronavirus precautions generally have caused delays to the commissioning of the other two machines, S67 and S68.
With 11 new stations and NATM-built connections, the UAG line will be located entirely underground at an average depth of around 30m. Istanbul’s mixed geology includes low-strength sandstones, siltstones, limestones and shales. To cope, the TBMs have been designed with versatile mixed-face, dome-style cutterheads with opening ratios of around 35%, and other features such as variable frequency electric drives and high-torque screw conveyors.
Working 24hours/day, the machines are installing 1,500mm wide by 300mm-thick pre-cast concrete lining rings comprising five segments plus key. Mucking is via continuous conveyor and materials are supplied from multi-service vehicles (MSVs). The TBMs performance has so far proved successful in the city. The UAG metro line is being constructed by the Gulermak, Nurol & Makyol JV.
